Apparatus and methods for handling workpieces in a processing system

ABSTRACT

Apparatus and methods for handling workpieces in a processing system. The workpiece vertical lift mechanism ( 200 ), which is disposed inside a process chamber ( 40 ) of the processing system, is adapted to transfer a workpiece ( 55 ) to and from a pedestal portion ( 286 ) of an electrode ( 24 ). The pedestal portion ( 286 ) is configured to support the workpiece ( 55 ) during processing. The workpiece vertical lift mechanism ( 200 ) including a workpiece fixture ( 290 ) movable relative to the pedestal portion ( 286 ) between a first position in which the workpiece fixture ( 290 ) holds the workpiece ( 55 ) in a non-contacting relationship with the pedestal portion ( 286 ) and a second position in which the pedestal portion ( 286 ) projects above workpiece fixture ( 290 ) so as to transfer the workpiece ( 55 ) from the workpiece fixture ( 290 ) to the pedestal portion ( 286 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/376,175,filed Feb. 3, 2009, which is the National Stage of InternationalApplication No. PCT/US07/76205, filed Aug. 17, 2007, which claims thebenefit of U.S. Provisional Application No. 60/823,175, filed Aug. 22,2006, the disclosure of each of which is hereby incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The invention generally relates to processing systems and, moreparticularly, to apparatus and methods for handling workpieces in aprocessing system.

BACKGROUND OF THE INVENTION

Processing systems, such as plasma processing tools, rely on holdingmechanisms to support a workpiece, such as a semiconductor, ceramic, ormetal substrate or wafer, inside a process chamber during theperformance of a treatment process. Certain holding mechanisms include aplurality of lift pins that are configured to raise or lower in unisonfor lifting and lowering the workpiece relative to a top surface of asupport. In the lowered position, the tips of the lift pins are eitherflush with, or slightly recessed below, the top surface of the supportso that the workpiece at least partially contacts the top surface. Inthe raised position, the tips of the lift pins contact a bottom surface(backside) of the workpiece and elevate the workpiece above the topsurface of the support. Typically, multiple lift pins establish multiplepoints of contact with the backside of the workpiece. The resulting gapbetween the lifted workpiece and the surface of the support permits anaccess space for insertion of an end effector.

The requirement for lift pins in conventional processing systemsnecessitates one or more mechanical feedthroughs in the process chamberfor transferring mechanical motion from a location outside of theprocess chamber to the lift pins. Each mechanical feedthrough requiresat least one port extending through the chamber wall of the processchamber. Each port provides a prime location for vacuum leaks. Moreover,contact between the lift pins and the workpiece may damage orcontaminate the backside of the workpiece. Further, the process ofraising and lowering the lift pins may generate particles thatcontaminate the process chamber and, if not remediated, eventually,result in contamination of the processed workpieces.

It would therefore be desirable to provide a workpiece vertical liftmechanism that addresses these and other deficiencies or challenges ofconventional processing systems.

SUMMARY

In an embodiment of the invention, an apparatus comprises a processchamber including upper and lower electrodes. A pedestal portion of thelower electrode is configured to support the workpiece duringprocessing. A workpiece vertical lift mechanism is disposed in theprocess chamber. The workpiece vertical lift mechanism includes avertically movable member disposed between the upper and lowerelectrodes. The vertically movable member is configured to movevertically relative to the pedestal portion of the lower electrodebetween first and second positions. In the first position, thevertically movable member holds the workpiece in a non-contactingrelationship with the pedestal portion. In the second position, thepedestal portion of the lower electrode projects above the first memberso as to transfer the workpiece from the first member to the pedestalportion.

In another embodiment, a processing method includes transferring aworkpiece to a vertically movable member inside a process chamber andthen moving the movable member vertically toward a pedestal portion of alower electrode so as to transfer the workpiece from the movable memberto the pedestal portion of the lower electrode. The method furthercomprises generating a plasma inside the process chamber using the lowerelectrode and an upper electrode, and processing the workpiece with theplasma while the workpiece is supported on the pedestal portion of thelower electrode.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description given below, serve to explain the principles ofthe embodiments of the invention.

FIG. 1 is a perspective view of a plasma processing system including aworkpiece vertical lift mechanism in accordance with an embodiment ofthe invention.

FIG. 2 is a front view of the plasma processing system of FIG. 1.

FIG. 3 is an exploded view of the enclosure and workpiece vertical liftmechanism of the plasma processing system of FIGS. 1 and 2.

FIG. 3A is another exploded view of the workpiece vertical liftmechanism of the plasma processing system of FIGS. 1, 2, and 3.

FIG. 4 is a cross-sectional view taken generally along line 4-4 in FIG.2.

FIG. 5 is a cross-sectional view similar to FIG. 4 in which the lid ofthe enclosure is in contact with the base of the enclosure.

FIG. 6 is an enlarged view of a portion of FIG. 4.

FIGS. 7-11 are perspective views similar to FIG. 1 illustrating theworkpiece loading process.

FIG. 12 is a perspective view showing a workpiece vertical liftmechanism in accordance with an alternative embodiment of the invention.

FIG. 13 is a perspective view of a workpiece vertical lift mechanism inaccordance with an alternative embodiment of the invention.

DETAILED DESCRIPTION

With reference to FIGS. 1-4, a plasma processing system 10 generallyincludes an enclosure 12 having a lid 14 and a base 16 upon which thelid 14 rests, support arms 18, 20 depending from the lid 14, an upperelectrode 22, a lower electrode 24, and a workpiece vertical liftmechanism 200 (FIG. 3A). The plasma processing system 10 furtherincludes a tubular separating member or ring 26 positioned between theupper and lower electrodes 22, 24 and contacting confronting faces aboutthe perimeter of the upper and lower electrodes 22, 24. The confrontingfaces of the upper and lower electrodes 22, 24 are generally planar andparallel plates and have approximately identical surface areas.

The support arms 18, 20 mechanically couple a housing 46 of the lid 14with a lifting device 28, illustrated in the representative embodimentas a pneumatic cylinder, which is configured to raise and lower the lid14 relative to the base 16 between a raised position (FIGS. 1, 2, 4) anda lowered position (FIGS. 5, 11). Alternatively, the lifting device 28may comprise a linear slide. When the lid 14 is in its lowered position,a conducting member 64 is captured between the respective perimeters ofthe lid 14 and base 16, which are metallic. The conducting member 64supplies a good electrical contact between the lid 14 and base 16 toestablish a conductive outer shell surrounding the upper and lowerelectrodes 22, 24.

The upper electrode 22 is suspended from the housing 46 of the lid 14 bya plurality of electrically insulating spacers, of which spacer 42 isvisible in FIG. 4. As a result, the upper electrode 22 moves along withthe housing 46 when the lid 14 is moved by the lifting device betweenthe raised and lowered positions relative to the base 16. When the lid14 is lowered into contact with the base 16 as shown in FIG. 5, asealing member 52 is compressed between the separating ring 26 and aperimeter of the lower electrode 24 to define a process chamber 40 (FIG.5). The process chamber 40 includes the volume or space bounded by theinwardly-facing horizontal surfaces of the upper and lower electrodes22, 24 and the inwardly-facing vertical surface of the sidewall definedby the separating ring 26.

In the raised position, unprocessed workpieces 55 can be transferred tothe workpiece vertical lift mechanism 200 and processed workpieces 55can be removed from the workpiece vertical lift mechanism 200. Theworkpiece vertical lift mechanism 200 is operative to facilitate theloading of workpieces 55 onto a pedestal portion 286 of the lowerelectrode 24 and the unloading of workpieces 55 from the pedestalportion 286 of the lower electrode 24. In the lowered position of thelid 14 and upper electrode 22, the process chamber 40 defines anenvironment that is suitable for plasma processing one of the workpieces55.

For in-line applications, the plasma processing system 10 may beprovided with an input carrier (not shown) that provides unprocessedworkpieces 55, an output carrier (not shown) that receives processedworkpieces 55, and an end effector 280 (FIG. 7) on an articulated arm ofa robot (not shown). The robot includes a series of actuators (notshown) that permit controlled, multi-axis articulated motion of thearticulated arm and end effector 280. The end effector 280 ismanipulated by the robot for transferring workpieces 55 from the inputcarrier to the process chamber 40 and from the process chamber 40 to theoutput carrier. In addition, a plurality of workpieces 55 may beintroduced in such a way that each individual workpiece 55 isindependently introduced into the plasma processing system 10 or in sucha way that multiple workpieces 55 are currently introduced into theplasma processing system 10. Individual workpieces 55 may also bepositioned on a support or carrier and transported thereon into theplasma processing system 10. The plasma processing system 10 maycomprise a single process station among multiple process stations thatcooperate to sequentially process multiple workpieces 55 moving in anassembly line fashion among the multiple process stations.

A power supply 30, which is coupled with the upper and lower electrodes22, 24 by shielded coaxial cables or transmission lines 32, 34,respectively, controls the power level and frequency of operation of theupper and lower electrodes 22, 24. The power supply 30 may be analternating current power supply operating at an extremely lowfrequency, such as 50 Hz and 60 Hz, at a high radio frequency, such as40 kHz and 13.56 MHz, at a medium radio frequency, such as 1 kHz, or ata microwave frequency, such as 2.4 GHz. The power supply 30 may alsooperate at dual frequencies superimposed upon one another.Alternatively, the power supply 30 may be a direct current (DC) powersupply in which the plasma is non-oscillating. In other alternativeembodiments, power supply 30 may supply a radio frequency (RF) powercomponent that provides a dense plasma and a DC power component thatindependently increases ion energy without affecting the plasma density.

In certain embodiments of the invention, the power supply 30 may operateat one or more radio frequencies and include an impedance matchingnetwork (not shown) that measures reflected power from the loadrepresented by the upper and lower electrodes 22, 24 and plasma confinedtherebetween back to the power supply 30. The impedance matching networkadjusts the frequency of operation of power supply 30 to minimize thereflected power. The construction of such matching networks isunderstood by a person of ordinary skill in the art. For example, theimpedance matching network may tune the matching network by changing thecapacitance of variable capacitors within the matching network to matchthe impedance of the power supply 30 to the impedance of the load as theload changes. The power and voltage levels and operating frequency(ies)may vary depending upon the particular application.

A vacuum pump 36 continuously pumps byproduct generated by the plasmaprocess and non-reacted process gas from the process chamber 40, whenthe plasma processing system 10 is operating, through a vacuum manifold38. A sealing member 50 (FIGS. 4 and 5) is compressed between theseparating ring 26 and the upper electrode 22. The vacuum pump 36 isoperative to maintain the total pressure in the process chamber 40 at asub-atmospheric level sufficiently low to promote plasma generation whenpower is applied by the operation of the upper and lower electrodes 22,24. Typical pressures suitable for plasma generation range from abouttwenty (20) millitorr to greater than about fifty (50) torr. Thepressure within the process chamber 40 is controlled in accordance witha particular desired plasma process and primarily consists of partialpressure contributions from the process gas, which may comprise one ormore individual gas species, supplied to the evacuated process chamber40.

A gas inlet plate 106 is fastened to an upper horizontal surface of theupper electrode 22. The gas inlet plate 106 is coupled by a gas port 112and a delivery line 113 with a process gas supply 114. A mass flowcontroller and a flow measurement device (not shown) may be providedthat cooperate to regulate the flow of each process gas from the processgas supply 114 to the gas port 112. The gas inlet plate 106 includesdistribution passages (not shown) and the upper electrode 22 includespassages (not shown) coupled with the distribution passages of the gasinlet plate 106. The passages in the upper electrode 22 communicate withthe process chamber 40 for injecting process gas into the processchamber.

The plasma processing system 10 includes a microprocessor-basedcontroller (not shown) that is programmed to control the operation of,among other components, the power supply 30, the vacuum pump 36, and theprocess gas supply 114. For example, the controller regulates the powerlevels, voltages, currents and frequencies of the power supply 30 andorchestrates the provision of process gas from process gas supply 114and the pumping rate of vacuum pump 36 to define a suitable pressure inprocess chamber 40 in accordance with the particular plasma process andapplication.

During processing of workpiece 55, the power applied between the upperand lower electrodes 22, 24 by power supply 30 produces anelectromagnetic field in the process chamber 40 defined between theupper and lower electrodes 22, 24 when the lid 14 and base 16 arecontacting and an environment suitable for plasma processing isprovided. The electromagnetic field excites the process gas present inthe processing region to a plasma state, which is sustained by theapplication of power from power supply 30 for the duration of the plasmatreatment.

A forced flow of an appropriate cooling fluid may be circulated throughthe air gaps between the upper and lower electrodes 22, 24 and theenclosure 12, such as air gap 56, for cooling the plasma processingsystem 10 and, in particular, for cooling the upper and lower electrodes22, 24. To that end, a fitting 57 (FIG. 2) may be provided in the lid 14to define a coolant port for coupling a coolant supply 59 (FIG. 2) withthese air gaps.

The upper and lower electrodes 22, 24 are formed from anelectrically-conductive material, such as aluminum. The separating ring26 is formed from a non-conducting dielectric material and isconstructed to be able to withstand the plasma environment inside theprocess chamber 40 without unduly contaminating the processed workpiece55. Generally, this implies that the material forming the separatingring 26 should be substantially resistant to etching by the plasmapresent in the process chamber 40. The separating ring 26 defines avertical sidewall of non-conductive material, in addition to providingthe vacuum seal between the upper and lower electrodes 22, 24.

Constituent species from the plasma contact and interact with exposedmaterial on the workpiece 55 to perform the desired surfacemodification. The plasma is configured to perform the desired surfacemodification of the workpiece 55 by selecting parameters such as thechemistry of the process gas, the pressure inside the process chamber40, and the amount of power and/or frequency applied to the upper andlower electrodes 22, 24. The plasma processing system 10 may include anend point recognition system (not shown) that automatically recognizeswhen a plasma process (e.g., an etching process) has reached apredetermined end point or, alternatively, plasma processes may be timedbased upon an empirically-determined process time.

With reference to FIGS. 3, 3A, 4, and 5 in which like reference numeralsrefer to like features in FIGS. 1 and 2, the workpiece vertical liftmechanism 200 generally includes a lift plate 202, a workpiece fixture290, a set of resiliently-biased supports 240 mechanically coupling theworkpiece fixture 290 with the lower electrode 24, and a set ofresiliently-biased push devices 258 projecting from the upper electrode22 toward the lower electrode 24 and the workpiece fixture 290. An outerperipheral edge or perimeter 274 of the workpiece fixture 290, which ispositioned between the upper and lower electrodes 22, 24, is encircledby the separating ring 26. After lid 14 is placed in the loweredposition contacting the base 16 to seal the process chamber 40 from theambient environment and the process chamber 40 is evacuated, theworkpiece vertical lift mechanism 200 resides within the evacuatedprocess chamber 40.

The workpiece fixture 290 includes a lift plate 202 and a workpiece ring204 that are joined, for example, by a pin-in-socket type engagement inwhich one of the lift plate 202 or workpiece ring 204 carries a set ofprojecting pins (not shown) and the other of the lift plate 202 orworkpiece ring 204 carries a set of sockets (not shown) that registerand mate with the pins. The workpiece fixture 290 is automaticallymoveable in conjunction with opening and closing the lid 14 and withoutoperator intervention between a raised position, when the lid 14 isopened, as best shown in FIG. 4, and a lowered position when the lid 14is in a closed position relative to the base 16, as best shown in FIG.5. In other words, the workpiece fixture 290 moves toward the loweredposition as the upper electrode 22 is moved by the lid 14 toward thelower electrode 24 to seal the process chamber 40 and moves toward theraised position as the upper electrode 22 is moved by the lid 14 awayfrom the lower electrode 24.

As best shown in FIGS. 3 and 3A, a cover plate 206 includes a cap 208and a support 210 that underlies the cap 208. The cap 208 may also bejoined with the support 210 by a pin-in-socket type engagement or,alternatively, the cap 208 and support 210 may constitute an integral,one-piece component. The cover plate 206 has a good electrical contactwith the lower electrode 24, as does the workpiece ring 204 and liftplate 202, when the lid 14 is lowered. As a result, the workpiecefixture 290 and the workpiece 55 are at approximately the sameelectrical potential as the lower electrode 24 when the plasmaprocessing system 10 is operating to generate a plasma inside theprocess chamber 40 and to process workpieces 55 inside the processchamber 40 with the plasma.

A recess 212 is located near each of the corners of the lower electrode24. Each recess 212 has a base 211 that represents a relatively thinwall of the material of lower electrode 24 remaining after therespective recess 212 is formed or machined in the lower electrode 24.Projecting from the base 211 of each of the recesses 212 is a mountingpost 214 with an internally threaded opening 216. Each mounting post 214may be positioned to be substantially coaxial with the respective one ofthe recesses 212. In the assembly forming the support 240, a threadedtip 218 of a guide pin 220 is mated with the internally threaded opening216 of each mounting post 214. The internally threaded opening 216 ofeach mounting post 214 is oriented such that the respective guide pin220 projects in a direction toward the lift plate 202.

Each of the recesses 212 is also bounded peripherally by a substantiallycylindrical sidewall 222 extending to the base 211 and a beveled orflared rim 224 disposed between sidewall 222 and a top surface 226 ofthe lower electrode 24. The diameter of the flared rim 224, whichintersects the top surface 226, is greater than the diameter of thesidewall 222 of each recess 212.

Each guide pin 220 includes a substantially cylindrical, non-threadedshank 228 extending from the threaded tip 218 toward a head 230. Thehead 230 may include a recessed feature 232 that receives the tip of atool (not shown) used to generate the mated engagement between thethreaded tip 218 of guide pin 220 and the internally-threaded opening216. The head 230 of each guide pin 220, which projects at leastpartially above the nearby top surface 226 of the lower electrode 24,carries a flared surface 225 located near the non-threaded shank 228.The non-threaded shank 228 of each guide pin 220 and the sidewall 222 ofthe respective recess 212 have a substantially coaxial arrangement.

Each of the supports 240 includes a stop block 242 coupled by arespective one of the guide pins 220 with the lift plate 202 of theworkpiece fixture 290. Each stop block 242 includes a body 244 with anenlarged head 246 and a central bore or passageway 248 extending thelength of the body 244. The radially outward projection of enlarged head246 relative to the body 244 defines an edge or lip 250, which extendscircumferentially about the body 244. The enlarged head 246 of each stopblock 242 further includes a first beveled or tapered exterior sidewall252 that decreases in diameter with increasing distance from the lip 250and a second beveled or tapered exterior sidewall 234 that increases indiameter with increasing distance from the lip 250. The exteriorsidewall 234 is disposed between the lip 250 and the tapered exteriorsidewall 252. The passageway 248 includes a substantially cylindricalsurface 236 and a beveled or tapered surface 238 that narrows a portionof the substantially cylindrical surface 236.

A flared recess 254 is defined near each of the peripheral corners ofthe lift plate 202. The tapered exterior sidewall 252 of each stop block242 is engaged with a respective one of the flared recesses 254. Thedepth of each flared recess 254 is selected such that a respectiveinclined surface 256 of the flared recess 254 and tapered exteriorsidewall 252 of each stop block 242 are contacting when the lift plate202 is secured with the stop blocks 242. The inclination angles of eachflared recess 254 and the corresponding tapered exterior sidewall 252 ofits stop block 242 are matched to assist in securing the stop blocks 242with the lift plate 202, yet permit ready removability of the lift plate202 by a vertical force of sufficient magnitude.

When mounted to the lift plate 202, the tapered surface 238 ofpassageway 248 in stop block 242 is located generally between one of therecesses 212 in the lower electrode 24 and the workpiece fixture 290.Disposed in each of the recesses 212 is a spring element 260, which mayhave the form of a compression spring formed from a helical coil ofwire. Each spring element 260 is confined within the respective recess212 and is captured between the base 211 and the lip 250 on therespective stop block 242.

As best shown in FIG. 6, the spring elements 260 are extended when theworkpiece fixture 290 is in the raised position. As a result, the liftplate 202 and workpiece ring 204 of the workpiece fixture 290 aresupported in a resiliently floating manner atop the supports 240. Underthe load supplied by the lift plate 202 and workpiece ring 204, thespring elements 260 collectively have a spring force sufficient tosuspend or elevate the lift plate 202 above the top surface 226 of lowerelectrode 24.

The tapered surface 238 contacts the flared surface 225 on the head 230of guide pin 220 to provide a positive stop for vertical motion when theworkpiece fixture 290 is in the raised position. The inclination anglesof the flared surface 225 and the tapered surface 238 are matched sothat each stop block 242 is self-centered on the respective guide pin220 when the workpiece fixture 290 is in the raised position. Thispermits the workpiece fixture 290 to return to a reproducible spatiallocation when residing in the raised position. In turn, this provides areproducible location within plasma processing system 10 for theworkpiece 55 carried by the workpiece fixture 290.

As explained in detail below, movement of the lid 14 to a loweredposition (FIG. 5) moves the workpiece fixture 290 toward a loweredposition and, thereby, compresses the spring elements 260. As theworkpiece fixture 290 is lowered, the head 230 of each of the guide pins220 moves in its respective passageway 248 toward the lift plate 202.

As best shown in FIGS. 3 and 3A, the workpiece fixture 290 includes acentral opening 270 extending entirely through the lift plate 202 andworkpiece ring 204, and a gap 272 that extends radially from the centralopening 270 to the outer perimeter 274 of the workpiece fixture 290. Thecover plate 206 is dimensioned with a width substantially identical tothe width of the gap 272. When the workpiece fixture 290 is lowered to aprocess position, the cover plate 206 fills the gap 272 so that thecentral opening 270 is surrounded by a substantially planar surfacedefined collectively by the top surface 266 of the workpiece ring 204and a top surface 276 of the cover plate 206. To promote the requisitecoplanar arrangement, the respective thicknesses of the cover plate 206and workpiece fixture 290 are selected to be approximately equal, whichpermits the top surfaces 266, 276 to be approximately flush when theworkpiece fixture 290 is in its lowered position. The central opening270 is round in the representative embodiment. However, the centralopening 270 may have other shapes, such as rectangular.

A shoulder or rim 278, which is defined in the workpiece ring 204,coaxially encircles the central opening 270. The radial dimension orwidth of the rim 278 is selected such that only a thin annular surfacearea on the workpiece 55 is contacted by the rim 278. For example, theradial dimension of the rim 278 may be approximately equal to 3 mm. Thediameter of the central opening 270 is approximately equal to thediameter of the workpiece 55 less the radial dimension of the rim 278.If the workpieces 55 are not round, the geometrical shape of the centralopening 270 is selected to conform to the shape of the workpiece 55. Therim 278 is recessed below the top surface 266 of the workpiece ring 204by an amount related to the thickness of the workpiece 55. Whenworkpiece 55 is resting on, and supported by, rim 278, a top surface ofthe workpiece 55 is approximately coplanar with the top surface 266 ofthe workpiece ring 204.

The width of the gap 272 is selected such that an end effector 280 (FIG.7) can pass through the gap 272 and access the central opening 270 fortransferring unprocessed workpieces 55 to the workpiece fixture 290 andremoving processed workpieces 55 from the workpiece fixture 290. The endeffector 280 is coupled with a robot, such as a selective compliantarticulated/assembly robot arm (SCARA) robot, as understood by a personhaving ordinary skill in the art.

The lower electrode 24 further comprises a removable electrode section284, which includes a mounting flange 285 situated in a recess definedin the lower electrode 24 and the pedestal portion 286. The pedestalportion 286, which defines representative a workpiece support, projectsfrom the mounting flange 285 toward the upper electrode 22. Theelectrode section 284 is secured with conventional fasteners to theunderlying and surrounding remainder of the lower electrode 24. The topsurface 226 of lower electrode 24 and the top surface 226 of themounting flange 285 are approximately flush. The surface area of a topsurface 288 of the pedestal portion 286, which is elevated above thesurrounding mounting flange 285, is approximately equal to the opencross-sectional area radially inside the central opening 270. Thediameter of the pedestal portion 286 is approximately equal to thediameter of the central opening 270 of workpiece ring 204. The electrodesection 284 has a good electrical contact with the remainder of thelower electrode 24 so that the pedestal portion 286 and support 210 areat substantially the same potential as the lower electrode 24 when theplasma processing system 10 is operating and a plasma is present in theprocess chamber 40.

The cover plate 206 comprises another raised region of the electrodesection 284 that projects above the plane of the mounting flange 285.The cover plate 206 and pedestal portion 286 may comprise a single orunitary raised region projecting from the mounting flange 285.Alternatively, the cover plate 206 may comprise a separate componentthat is mounted to the electrode section 284 and, in this instance, mayinclude locating pins (not shown) or the like used to automaticallyposition the cover plate 206 relative to the central opening 270 in theworkpiece fixture 290.

When the workpiece fixture 290 is lowered to a process position, contactbetween the workpiece 55 and the top surface 288 of pedestal portion 286transfers the workpiece 55 from the workpiece ring 204 to the pedestalportion 286. The transfer of the workpiece 55 is accomplished withoutany structure on the pedestal portion 286, the lower electrode 24, orthe base 16 of the enclosure 12 guiding of the workpiece 55 onto thepedestal portion 286. In the lowered process position of the workpiecefixture 290, the top surface 266 of workpiece ring 204 is recessedslightly below the top surface 288 of the pedestal portion 286. Duringplasma treatment, the workpiece 55 rests on the top surface 288 of thepedestal portion 286.

The electrode section 284 and the lift plate 202 are constructed from anelectrical conductor, such as aluminum. The cap 208 on the cover plate206 and the workpiece ring 204 are constructed from an electricalinsulator or dielectric, such as alumina or high-purity alumina.Alternatively, the cap 208 on the cover plate 206 and the workpiece ring204 may also be constructed from an electrical conductor, such asaluminum. The selection of a constituent material for the cap 208 of thecover plate 206 and the workpiece ring 204 is dictated by the type ofplasma performance required in the plasma processing system 10 for aparticular plasma process on workpiece 55. Although not wishing to bebound by theory, it is believed that constructing the cap 208 of thecover plate 206 and workpiece ring 204 from an electrical conductoroptimizes etch rate driven plasma processes or treatments and thatconstructing the cap 208 of the cover plate 206 and workpiece ring 204from a dielectric optimizes uniformity driven plasma processes.

With reference to FIGS. 3A and 4, one of the push devices 258 is locatedspatially near each inside corner 15 of separating ring 26 and, asapparent, near each corresponding outside corner (not shown) of theupper electrode 22. Each of the push devices 258 includes a pusher block262, which is secured with the upper electrode 22 by the cooperationbetween an insert 261 and a shoulder bolt 263, and a spring element 264.Each of the pusher blocks 262 has a substantially overlying relationshipwith a respective one of the stop blocks 242. One end of the springelement 264, which may have the form of a compression spring formed froma helical coil of wire, is captured between an enlarged head 265 of thepusher block 262 and the upper electrode 22. The pusher block 262 isconstructed from an insulating or dielectric material, such as aceramic, and the insert 261 and shoulder bolt 263 may be formed from ametal, such as a stainless steel. The shoulder bolt 263 has a threadedtip that is fastened in a threaded bolthole in the upper electrode 22.The pusher block 262 of each push device 258 is movable relative to theshoulder bolt 263 between a first position (FIG. 4) in which the springelement 264 is extended and a second position (FIG. 5) in which thespring element 264 is compressed. The spring element 264 supplies apreloaded bias to each pusher block 262 in the first position.

As the lid 14 is moved toward the base 16, the pusher block 262 of eachof the push devices 258 contacts the top surface 266 of workpiece ring204 and the spring elements 264 begin to compress. As the lid 14approaches the base 16, the spring elements 264 are further compressed,which applies an increasing force to the workpiece ring 204 that causesthe workpiece fixture 290 to move toward the top surface 288 of thepedestal portion 286 and toward the lower electrode 24. When theworkpiece fixture 290 is in the lowered position, the tapered exteriorsidewall 234 on each stop block 242 contacts the flared rim 224 ofrecess 212 and each pusher block 262 is moved to its second position.

The inclination angles of the flared rim 224 and tapered exteriorsidewall 234 are approximately equal or matched. When the workpiecefixture 290 is in the lowered position, each of the flared rims 224 isin contact with the respective one of the exterior sidewalls 234. Thecontact automatically self-centers each stop block 242 within itsrespective recess 212. Consequently, each time that the lid 14 islowered, the workpiece fixture 290 returns to a reproducible spatiallocation relative to the lower electrode 24 and removable electrodesection 284 when the lid 14 moves the workpiece fixture 290 to thelowered position. In turn, this provides a reproducible location forsuccessive workpieces 55 on the pedestal portion 286 during eachsequential plasma treatments.

In use and with reference to FIGS. 1, 2, 3, 3A, and 4-11, the lid 14 islifted to an open position relative to the base 16 (FIGS. 2, 7) andplaced out of contact with the base 16. With the lid 14 lifted, thecomponents of the workpiece vertical lift mechanism 200 have an initialarrangement as best shown in FIG. 4. The spring-biased supports 240 urgethe workpiece fixture 290 away from the lower electrode 24 to providethe raised position. When the workpiece fixture 290 is in the raisedposition and contact is established between the tapered surface 225 andflared surface 238 of each spring-biased support 240, a reproduciblelocation is defined for the central opening 270 so that the end effector280 can reproducibly place workpieces 55 on the workpiece fixture 290.

The end effector 280 is manipulated to transport one of the workpieces55 to a location near to the plasma processing system 10, as shown inFIG. 7. The end effector 280 moves the workpiece 55 from this location,which is outside of the enclosure 12, to a position between the upperand lower electrodes 22, 24 and above the central opening 270, as shownin FIG. 8. When the workpiece 55 is transferred by the end effector 280from the location outside of the enclosure into the position above thecentral opening 270 of the workpiece fixture 290, the workpiece 55 isnot guided by any structure associated with the enclosure 12, such asrails or another type of mechanical constraint, associated with the base16 of enclosure 12.

The end effector 280 is lowered so that the outer periphery of theworkpiece 55 contacts the rim 278 inside the central opening 270 ofworkpiece ring 204, as shown in FIG. 9. The workpiece 55 is then fullysupported on the rim 278. After the workpiece 55 is transferred to theworkpiece fixture 290, the end effector 280 is withdrawn through the gap272 to a location completely outside of the footprint of the lid 14 andbase 16, as shown in FIG. 10. The end effector 280 physically fitswithin the gap 272 during this sequence of motions. The outer peripheryof the workpiece 55 is supported by contact with the rim 278 of centralopening 270 and is suspended above the lower electrode 24.

The lid 14 is lowered relative to the base 16, as shown in FIG. 10, andeventually contacts the base 16 to establish the closed position, asshown in FIG. 11. Lowering the lid 14 moves the upper electrode 22toward the lower electrode 24. As the lid 14 is lowered toward theclosed position, the pusher blocks 262 projecting from the upperelectrode 22 contact the top surface 266 of the workpiece ring 204. Thecontact causes the spring elements 264 to compress, which applies a biasforce to the workpiece fixture 290. The applied bias force from thespring elements 264 of the push devices 258 overcomes the opposingspring bias of the supports 240 and moves the workpiece fixture 290toward the lower electrode 24. The motion of the workpiece 55 on theworkpiece fixture 290 is in a vertical direction relative to the base 16of the enclosure 12 and toward the lower electrode 24, and fails toinclude any significant motion component in a horizontal directionrelative to the base 16.

Each guide pin 220 has a non-contacting relationship with the respectivestop block 242 as the workpiece fixture 290 moves between the raised andlowered positions. As the workpiece fixture 290 nears the fully loweredposition and the spring-biased supports 240 yields toward the lowerelectrode 24, the workpiece 55 is transferred from the rim 278 ofworkpiece ring 204 to the pedestal portion 286 of the lower electrode24. At the fully lowered position of the workpiece fixture 290, theworkpiece 55 rests on the pedestal portion 286 of the lower electrode 24and a small clearance (e.g., 2 or 3 mils) exists between the rim 278 ofworkpiece ring 204 and the workpiece 55.

The process chamber 40 is evacuated using vacuum pump 36 and process gasis introduced from the gas inlet plate 106 to establish a suitablepressure. The upper and lower electrodes 22, 24 are energized by powersupply 30 to generate a plasma from the sub-atmospheric pressure ofprocess gas in the process chamber 40. When the plasma treatment ofworkpiece 55 is completed, the process chamber 40 is vented and the lid14 of enclosure 12 is raised. Movement of the upper electrode 22 awayfrom the lower electrode 24 opens the process chamber and eventuallyremoves the contact between push devices 258 and the top surface 266 ofworkpiece ring 204. As a result, the force urging the workpiece fixture290 toward the lower electrode 24 is gradually removed. The springelements 260 of the spring-biased supports 240 are released to expand totheir uncompressed state, which automatically elevates and restores theworkpiece fixture 290 to the raised position. The motion of theworkpiece 55 on the workpiece fixture 290 is in a vertical directionrelative to the base 16 of the enclosure 12 and toward the upperelectrode 22, and does not include any motion component in a horizontaldirection relative to the base 16. The workpiece 55 is transferred fromthe pedestal portion 286 of the lower electrode 24 back to the rim 278of workpiece ring 204.

As the raised position is approached, the tapered surface 225 and flaredsurface 238 of each spring-biased support 240 reestablish contact toagain define the reproducible location for the central opening 270. Theseparation between the lower electrode 24 and the central opening 270 ofthe workpiece fixture 290 provides an open space for the end effector280 to gain access to the backside of each processed workpiece 55, liftthe processed workpiece 55 from the central opening 270, and withdrawthe processed workpiece 55 from the plasma processing system 10. The endeffector 280 physically fits within the gap 272 during this sequence ofmotions. When the workpiece 55 is retrieved by the end effector 280 fromthe position within the central opening 270, the workpiece 55 is notguided by any structure associated with the enclosure 12.

The workpiece vertical lift mechanism 200 maintains a parallel platedesign of the plasma processing system 10 while the plasma treatmentoccurs. The workpiece vertical lift mechanism 200 presents a passivewafer chucking system that eliminates the need for active mechanicalassistance, such as mechanically- or electrically-actuated lift pins.This simplifies the design of the plasma processing system 10 becausethe workpiece vertical lift mechanism 200 eliminates the need formechanical feedthroughs, and the like, that are characteristic of activewafer chucking systems with a concomitant cost reduction. The design ofworkpiece vertical lift mechanism 200 readily permits modifications tohandle workpieces 55 of different dimensions. The workpiece verticallift mechanism 200 may be retrofitted to existing plasma processingsystems. Device regions of the workpiece 55 are not contacted by liftpins or any other mechanical structure during workpiece exchanges.Instead, the workpiece fixture 290 permits the workpiece 55 to be liftedand lowered by contact only between rim 278 and a narrow annular bandnear the workpiece's peripheral edge.

In an alternative embodiment, the separating ring 26 may be omitted andthe interior of the enclosure 12 may be otherwise configured to define avolume that is evacuated by the vacuum pump 36 to define a processchamber similar to process chamber 40. In this instance, the upper andlower electrodes 22, 24 are resident in the process chamber 40. Inanother alternative embodiment, the upper electrode 22 and the lid 14may be consolidated into a unitary structure in which all or a portionof the lid 14 operates as an electrode.

The lift plate 202 and workpiece ring 204 of the workpiece fixture 290,the removable electrode section 284 and its pedestal 286, and the coverplate 206 may be collectively replaced as a component set to adapt theworkpiece vertical lift mechanism 200 to handle workpieces 55 ofdifferent sizes and/or geometrical shapes.

As shown in FIG. 12 in which like reference numerals refer to likefeatures in FIGS. 1-11 and in accordance with an alternative embodiment,a workpiece fixture 290 a includes a lift plate 202 a and a workpiecering 204 a that are similar in construction to lift plate 202 andworkpiece ring 204. The workpiece fixture 290 a has a round centralopening 270 a and a rim 278 a of a different diameter than therespective central opening 270 and rim 278 of workpiece fixture 290(FIG. 3) for accommodating a workpiece 55 a with the representative diskshape and characterized by a different diameter than workpiece 55. Thereplacement entails removing the assembly consisting of the lift plate202 and workpiece ring 204 of workpiece fixture 290 from the lowerelectrode 24 with a lifting force of a magnitude effective to disengagethe flared recesses 254 from the corresponding tapered exterior sidewall252 of the respective stop blocks 242. The replacement workpiece fixture290 a is installed by engaging the flared recesses (not shown) in thelift plate 202 a, which are similar to the flared recesses 254 in liftplate 202, with the same supports 240. The guide pins 220 and stopblocks 242 are capable of being universally used with each of theworkpiece fixtures 290, 290 a. All that is required is to establish aphysical connection between the supports 240 and the specific one of theworkpiece fixtures 290, 290 a installed in the plasma processing system10.

A new removable electrode section 284 a is installed, as a replacementfor electrode section 284, that includes a pedestal portion 286 adimensioned diametrically to fit within the central opening 270 a. Inthe representative embodiment, the outer diameter of pedestal portion286 a is slightly less than the inner diameter of the round centralopening 270 a. A cover plate 206 a, which is similar to cover plate 206,is disposed in a gap 272 a, which is similar to gap 272 but slightlywider due to the larger dimensions of the central opening. The pusherblocks 262, which remain the same, move the workpiece fixture 290 abetween the raised and lowered positions in conjunction with the openingand closing of the lid 14. When the workpiece fixture 290 a is in thelowered position, a top surface 266 a of workpiece fixture 290 a and atop surface 276 a of cover plate 206 a are approximately coplanar andthe pedestal portion 286 a projects slightly above the top surfaces 276a and 288 a. As a result, the workpiece 55 a contacts and is supportedby a top surface 288 a of the pedestal portion 286 a.

Additional workpiece fixtures, cover plates, and electrode sections (notshown) may be supplied that are substantially identical to workpiecefixtures 290, 290 a, cover plates 206, 206 a, and electrode sections284, 284 a, but in which these components cooperate to accommodateround, disk-shaped workpieces of different diameters. For example, a setof four different component sets may be provided for use with the plasmaprocessing system 10 to support 100 mm, 150 mm, 200 mm and 300 mmwafers, respectively, by simply replacing the workpiece fixture, coverplate, and electrode section.

With reference to FIG. 13 in which like reference numerals refer to likefeatures in FIGS. 1-12 and in an alternative embodiment, a compressionring 300 may be carried by the lid 14 that, when the lid 14 is closed,contacts the workpiece 55 to establish a seal encircling the outerperimeter of the workpiece 55 and press the workpiece 55 downward towardthe pedestal portion 286. The compression ring 300 includes perforations302 for the passage of gases that permit the process chamber 40 to beevacuated by vacuum pump 36.

References herein to terms such as “vertical”, “horizontal”, etc. aremade by way of example, and not by way of limitation, to establish athree-dimensional frame of reference. Terms, such as “upper”, “lower”,“on”, “above”, “below”, “side” (as in “sidewall”), “higher”, “lower”,“over”, “beneath” and “under”, are defined with respect to thehorizontal plane. It is understood that various other frames ofreference may be employed without departing from the spirit and scope ofthe invention as a person of ordinary skill will appreciate that thedefined frame of reference is relative as opposed to absolute.

While the invention has been illustrated by a description of variousembodiments and while these embodiments have been described inconsiderable detail, it is not the intention of the applicants torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. The invention in its broader aspects istherefore not limited to the specific details, representative apparatusand methods, and illustrative examples shown and described. Accordingly,departures may be made from such details without departing from thespirit or scope of applicant's general inventive concept. The scope ofthe invention itself should only be defined by the appended claims.

1. A method of processing a workpiece supported on a pedestal portion ofa lower electrode in a process chamber of a processing system, themethod comprising: transferring a workpiece to a lift plate inside theprocess chamber; moving the lift plate vertically toward the pedestalportion of the lower electrode so as to transfer the workpiece from thelift plate to the pedestal portion; generating a plasma inside theprocess chamber using the lower electrode and an upper electrode; andprocessing the workpiece with the plasma while the workpiece issupported on the pedestal portion of the lower electrode.
 2. The methodof claim 1 wherein the processing system includes the upper electrode ismovable toward said lower electrode, and moving the lift plate towardthe pedestal portion further comprises: moving the upper electrodetoward the lower electrode; and transferring a force from the upperelectrode to the lift plate, as the upper electrode moves toward thelower electrode, effective to move the lift plate toward the pedestalportion.
 3. The method of claim 2 further comprising: after processingthe workpiece, moving the upper electrode away from the lower electrodeso as to release the force transferred from the upper electrode to thelift plate; and resiliently biasing the lift plate away from the lowerelectrode, as the force is released, so that the workpiece istransferred from the pedestal portion to the lift plate.
 4. The methodof claim 2 wherein the process chamber includes a base and a lid movablerelative to the base between an open position in which the lid isseparated from the base and a closed position in which the lid isproximate to the base, the upper electrode is mounted to the lid, andtransferring the workpiece from the lift plate to the pedestal portionfurther comprises: moving the lift plate relative to the pedestalportion by contact with the lid, as the lid is moved from the openposition toward the closed position, to transfer the workpiece from thelift plate to the pedestal portion.
 5. The method of claim 2 furthercomprising: after processing the workpiece, releasing the forcetransferred from the upper electrode to the lift plate; and resilientlybiasing the lift plate away from the lower electrode, as the force isreleased, so that the workpiece is transferred from the pedestal portionto the lift plate.
 6. The method of claim 1 further comprising: afterprocessing the workpiece, resiliently biasing the lift plate away fromthe pedestal portion so that the workpiece is transferred from thepedestal portion to the lift plate.
 7. The method of claim 1 whereintransferring the workpiece to the lift plate further comprises:supporting the workpiece on an end effector; and manipulating the endeffector carrying the supported workpiece to transfer the workpiece froma position outside of the process chamber to the lift plate and withoutguiding the workpiece during the transfer.
 8. The method of claim 7further comprising: after processing the workpiece, manipulating the endeffector to remove the workpiece from the lift plate and to the positionoutside of the process chamber.
 9. The method of claim 7 the workpieceis removed to the position outside of the process chamber withoutguiding the workpiece during the transfer.